The invention relates to a ferrule in particular for use in a pluggable connection for at least two multiple optical fibers to be connected to each other and each including at least two optical waveguides.
The ferrules of the type concerned are also referred to as multiple optical plugs. These multiple optical plugs are used for connecting multiple optical fibers. Multiple optical fibers comprise a plurality of waveguides that may be connected to individual waveguides of an additional multiple optical fiber. To this end, the individual waveguides are spread apart at the end of each multiple optical fiber and accommodated in a ferrule each. The ferrules are designed such that the individual waveguides of a multiple optical fiber are held in a defined direction and at a defined position. Accordingly, by joining together the face sides of two ferrules, the individual optical waveguides of the multiple optical fibers disposed in the two ferrules may be arranged opposite each other such that the optical waves of one optical waveguide each of the first multiple optical fiber are each fed into an associated optical waveguide of the second multiple optical fiber.
With the known multiple optical plugs, there is the problem that the transmission performance between two apparatus connected by multiple optical fibers is limited. In addition thereto, during transmission of information between two such apparatus, there may arise transmission errors that are due to the pluggable connection between two multiple optical fibers.
It is thus an object of the invention to make available a ferrule or multiple optical plug of the type concerned, which permits transmission of information with high performance and high reliability.
This object is met by the subject matter of the independent claims. Advantageous further developments are indicated in the respective dependent claims.
According to the invention, the ferrule comprises a plug housing adapted to be inserted into a ferrule container in a direction of insertion and/or to be mated with an additional plug housing, with the plug housing according to the invention having at least two receiving portions for receiving one multiple optical waveguide each.
Due to the design of the ferrule according to the invention with at least two receiving portions for multiple fibers, it is ensured that considerably more individual optical waveguides can be accommodated in the ferrule as compared to known ferrules. The transmission speed of information between apparatus interconnected via multiple optical fibers is thus increased.
The receiving portions provided according to the invention advantageously are arranged beside each other and/or above each other as seen in direction of insertion, with the possibility of arranging the receiving portions in offset manner from each other, in a direction transversely to the direction of insertion, with respect to a line of symmetry of the plug housing. This leads to a particularly high optical waveguide density on a face side of the ferrule according to the invention.
In particular for connecting two plug housings to each other, there may be provided guide bores extending in the direction of insertion, which may be provided with guide pins. These guide bores may also be offset from each other in a direction transversely to the direction of insertion with respect to a line of symmetry of the plug housing, which turns out to be advantageous especially if at least two receiving portions are arranged offset from each other in a direction transversely to the direction of insertion.
The invention is also realized by a ferrule having a plug housing with known function, in which is provided at least one receiving portion for receiving a multiple optical waveguide. For the plug housing according to the invention, there is used thermoplastic plastics material having filler particles admixed therein. Such thermoplastic plastics material is also referred to as matrix with the fillers being provided to reduce the amount of matrix required.
According to the invention, there are provided filler particles having a longitudinal direction of extension, which may extend at least in part transversely to a direction of insertion of the ferrule and at least in part parallel to the direction of insertion, respectively. This results in a ferrule according to the invention with particularly good thermal properties.
Such a ferrule, on at least one side of the plug housing, may have a casting compound entry region, and on a side of the plug housing opposite this casting compound entry region, there may be provided a casting compound exit region. A connecting line between casting compound entry region and casting compound exit region runs parallel to the direction of extension of elongate filler particles provided in a surrounding region of the receiving portion.
Differently therefrom or in addition thereto, the plug housing may have a casting compound entry region on at least one side, with a flow barrier incision in the plug housing being provided between at least one side of the plug housing opposite the casting compound entry region and the casting compound entry region proper. The flow barrier incision is formed as a constriction of the plug housing in a direction transversely to the direction of insertion. A connecting line between the casting compound entry region and the flow barrier incision runs parallel to the direction of extension of elongate filler particles provided in the surroundings of the receiving portion.
The invention is based on the finding that particularly good thermal properties and thus particularly high transmission quality can be achieved if the surroundings of the receiving portion have elongate filler particles provided therein which extend both parallel to each other and preferably transversely to the connecting line of V-shaped grooves in a receiving portion of the ferrule.
The receiving portion may have waveguide grooves extending in the direction of insertion and it may be designed to be closed by a cover. This provides for particularly simple assembly of the ferrule according to the invention. In this respect, it is particularly advantageous if the receiving portion has a dovetail guide means for fixing the cover.
The invention also is realized in a. combination of the features of the independent claims. It is of relevance in this respect that in particular a plug housing with at least two receiving portions for receiving one multiple optical waveguide each can be provided in particularly reliable manner if the plug housing is made of thermoplastic plastics material having elongate filler particles admixed thereto, with the direction of longitudinal extension thereof extending at least in part transversely and in part parallel to the direction of insertion, respectively. Differently therefrom, the plug housing may also be made from thermosetting plastics material, retaining the other features.
The invention also is realized in the form of a method of making a ferrule according to the invention which makes use of a correspondingly designed injection mold.
The multiple optical plugs according to the invention, in particular, are also made from a thermoplastics or thermosetting plastics material highly filled with spherical quartz globes. The multiple optical plug according to the invention, made from thermoplastic plastics material, also works over the entire range of operating temperatures in combination with a multiple optical plug of thermosetting plastics material, also in case of different temperatures of the two mating partners.
One of the fundamental ideas of the present invention is based on the finding that the problems existing in connection with the known ferrules can be solved by way of procedural technology and by selection of suitable thermoplastic plastics materials and suitable fillers.
According to the invention, the thermoplastic plastics material of the ferrule according to the invention comprises at least one partly crystalline thermoplastic material. For example, there are provided in particular Liquid Crystal Polymer (LCP), poly (phenylene sulphide) (PPS), or poly (ether ether keytone) (PEEK).
In addition thereto, there may be provided a filler designed as a reinforcing material, such as e.g. glass, carbon, aramide and/or steel fibers. The fibers of the reinforcing material are designed to have a predetermined diameter/length ratio. For example, there may be provided fibers which, with a diameter of approx. 10 xcexcm to approx. 20 xcexcm, have a length of approx. 300 xcexcm.
In addition thereto, there may also be provided fillers in the form of spherical mineral fillers. Such mineral fillers may have a diameter from approx. 2 xcexcm to approx. 8 xcexcmm. These fillers then improve the shrinkage behavior during manufacture of the ferrule according to the invention, which has a particularly favorable effect on the dimensional accuracy in particular in the entire range of operating temperatures. According to the invention, the addition of glass fibers and mineral fillers may take place in a weight ratio of approx. 2:3, aiming at maximum filling of the basic material for making the ferrule according to the invention.
According to the invention, it is possible to influence a specific coefficient of expansion of the ferrule according to the invention also by way of the orientation of the molten plastics material in an injection mold used for making the ferrule. If plastics macro-molecules and fillers, in particular glass fibers formed during solidification of the molten plastics material are aligned, a finding underlying the invention has revealed that a lower coefficient of thermal expansion is present in the direction of the glass fibers and plastics macro-molecules than in a direction perpendicular thereto. Of decisive significance for the operability of the ferrule according to the invention is a region between cylindrical openings for centering pins, which is also referred to as receiving portion for the optical waveguides, since utmost positional accuracy is necessary here. The orientation of the plastics macro-molecules and fillers in this region may also be obtained by the shape and position of a sprue or gating and by the design of a so-called mold void. Film gating at least over the length of a substantial microstructure, such as a receiving portion for optical waveguides, or also over the entire component length, with small cross-sectional area of the sprue or gating and central gating position on a side face, effects an inflow of molten plastics material in the form of a front parallel to a side face, as well as shearing of the molten plastics material and formation of a free jet. By these measures, the molten plastics material is oriented already at the time of injection in line with the optical waveguide fiber arrangement, i.e. especially perpendicularly to the optical waveguides in the receiving portion. To improve the orientation in the relevant region around the receiving portion, the molten plastics material is moved in the direction of injection until shortly before solidification thereof. When using a so-called xe2x80x9clost or broken moldxe2x80x9d opposite the sprue portion or by provision of flow deceleration means in the casting tool subsequent to the receiving portion, a sufficient aligning effect may be achieved. Preferably, the casting volume behind the flow deceleration means or the xe2x80x9clost moldxe2x80x9d is equal to or greater than the region of the mold constituting the relevant portion of the plastics core.
The ferrule according to the invention makes available a connecting plug of an inexpensive thermoplastic material that distinguishes itself by low material costs and low tool costs. In addition thereto, short cycle times may be achieved, and by suitable choice of the material, lower sensitivity to breakage and thus a higher number of insertion cycles of the ferrule according to the invention can be obtained.
According to the invention, the following exemplary filler and reinforcing materials are feasible: LCP +50n%, PPS +65%, PEEK +50% filler and reinforcing materials.
The ferrule according to the invention, comprising at least two or more receiving portions for receiving one multiple optical waveguide each, with a face area of the ferrule of 16 mm2, may accommodate a total of 12 individual optical waveguides in a grid element spacing of 0.25 mm. Accordingly, when two receiving portions are employed, up to 32 individual optical waveguides can be accommodated. The outer contour, the contact face and optionally the guide members remain the same as compared to the so-called MT standard. Coding of the direction of insertion of the ferrule according to the invention may be realized with the aid of chamfers or by means of different diameters of guide pins.
Differently therefrom, 24-pole MT plugs or MT ferrules may be provided as well.